Josephson结中激发孤子的电流脉冲方法──原理与数值实验

根据反散射理论讨论了电流脉冲法产生磁通孤子的阈值条件。对甚长结作的数值实验与理论符合很好。对有限结，考虑到边界效应，电流台阶范围等因素，对孤子激发条件有额外的要求，对圆对称环域结用脉冲法激发了孤子，并分析了其中回波效应、外磁场等对激发条件的影响。所有结果表明，电流脉冲法是在Ｊｏｓｅｐｈｓｏｎ结中激发孤子态的有效方法，理论阈值条件可以提供有益的参考作用。

FLUXON GENERATION BY A CURRENT PULSE IN JOSEPHSON JUNCTIONS──THEORY AND SIMULATIONS

The problem of fluxon generation in Josephson junctions by a current pulse is addressed, with the help of the inverse scattering transform theory. The threshold conditions for soliton (breather or fluxon) generation are obtained analytically, with respect to relevant studies in the same direction. The reliability of the theory is examined by direct numerical experiments. Fairly good agreements exist between the theory and the numerical results, particularly in the case of semi-infinitely long junctions. Practically long (L～10λ) Josephson junctions are also explored, namely, overlap, in-line and circularly-symmetric annular junctions. Explained are those factors that complicate the generation processes suck as boundary effects, stability of soliton states against the driving current, soliton return effect and the applied magnetic field (in annular junctions only). The current pulse method is shown to be effective and practical for fluxon generation in Josephson junctions.